1. Technical Field
Embodiments of the present invention relates to a converter.
2. Description of the Related Art
In accordance with current trends, in terms of electronic and communication devices, a system part has been rapidly miniaturized and lightweight together with the development of a semiconductor integrated circuit, but a power part has not been miniaturized and lightweight compared with what expected due to an energy storage device such as an inductor, a capacitor, etc.
Accordingly, in order to meet the current trends of miniaturized and lightweight electronic and communication devices, it is very important to obtain a miniaturized and lightweight converter used for a power device, in particular, a switching mode power supply (SMPS), etc.
In the converter used in the SMPS, etc., as a switching frequency is increased, capacity of an energy storage device is capable of being reduced, thereby obtaining a miniaturized and lightweight converter via high-speed switching.
However, when a switching frequency is increased using a high-speed semiconductor switching device, etc., switching loss and a heating issue of the switching device are caused.
Recently, in order to overcome this problem, a so-called soft-switching method has been proposed. According to the soft-switching method, when a voltage between opposite ends of the switching device reaches a zero point or a lowest point of a resonance waveform, switching loss becomes 0 (which materially includes a scope close to 0) by turning on the switching device.
However, according to the soft-switching method, when an output voltage of a converter does not reach a sufficient level, a voltage between opposite ends of the switching device does not resonate, and thus a switching operation is not capable of being performed.
Accordingly, a converter using the soft-switching method is not capable of performing a voltage boosting operation during startup (which also includes a procedure in which power is supplied and increased to a sufficient output level and restart as well as initial startup), thereby reducing the reliability of an SMPS itself.